1. Field of the Invention
This invention relates to water-based functional fluids thickened by an associative polyether thickener whose thickening power is enhanced by the addition of certain quaternary ammonium salts.
2. Description of the Prior Art
U.S. Pat. No. 4,411,819 discloses the advantages of using associative polyether thickeners to thicken waterbased functional fluids. Although these thickeners have excellent thickening ability, they are expensive and new methods for decreasing the amount of such thickeners have been explored. For instance, U.S. Pat. No. 4,312,775 discloses that reduced amounts of associative polyether thickener can be used in conjunction with ethoxylated phosphate ester.